Over the decades, textile printing and dyeing industry has long been one of the real economy in China with flourishing development, which has laid a solid foundation in the past few decades for the economic development in China, as a result it has accounted for a remarkable growth of Gross Domestic Product (GDP). So far, China is well known as the largest exporter of textile products, and the textile printing and dyeing industry is one of the top earners of foreign currency. However, the textile printing and dyeing industry is also considered a typical high-polluting industry, because the printing and dyeing process requires large quantities of water and high energy, leading to large wastewater discharge and high pollution, therefore it has caused serious environmental problems. Meanwhile, the major factor associated with the environmental pollution is the large quantity of effluent discharge. It is because the wet processing of textile materials usually cannot take full advantage of the dosing of the dyeing chemicals. For instance, depending on different processes applied, dyeing 1 kg of cotton fabric with reactive dye requires about 70-150 kg of water. Despite the gradual improvement of the dyeing process and technology, there are about 10-40% of the reactive dyes that cannot be fully fixed to the fabric due to various reasons during the processing. These dyes are hydrolyzed afterwards and cannot be recycled, then it is usually discharged with dyeing wastewater. Since the waste effluents are colored and highly polluting, discharging untreated wastewater to the environment would cause serious ecological pollution problems. Therefore, appropriate wastewater treatment processes are essential.
The most conventional treatment of dyeing and printing wastewater is based on biological treatment. Due to lower handling cost, biological treatment has always been the preferred processes for the majority of treatment plants. However, one of the most outstanding shortcomings of this technique is that it requires lengthy processing time, which results in unsatisfactory efficiency. Furthermore, there is more strict discharge standards for printing and dyeing wastewater, so that the effectiveness of the biological treatment is gradually weakened. In recent years, processes and techniques based on advanced oxidation processes (AOPs) have been developed, including UV photocatalysts, catalytic ozonation and electrochemical oxidation etc. Among these techniques, catalytic ozonation has relatively better application prospect when compared with other methods. However, high energy consumption in oxidation by catalytic ozonation has always been the major issue. One of the most important technical barrier is the development of efficient catalysts, while improving ozonation efficiency for various organic pollutants and ensuring the enhanced catalytic degradation with reduced ozone consumption, how to avoid catalyst poisoning is a big engineering challenge.